CN114053887B - Composite reverse osmosis membrane based on water-soluble polymer and preparation method thereof - Google Patents
Composite reverse osmosis membrane based on water-soluble polymer and preparation method thereof Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/56—Polyamides, e.g. polyester-amides
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
- B01D61/025—Reverse osmosis; Hyperfiltration
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/12—Composite membranes; Ultra-thin membranes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/124—Water desalination
- Y02A20/131—Reverse-osmosis
Abstract
The invention discloses a composite reverse osmosis membrane based on a water-soluble polymer and a preparation method thereof. The method comprises the following steps: step 1: placing the base support membrane in the aqueous phase solution for dipping for 1-2 minutes, and removing the redundant aqueous phase solution; transferring the mixture into an oil phase solution for interfacial polymerization for 2-3 minutes; activating in n-hexane extractive solution; drying to obtain a polyamide reverse osmosis membrane; step 2: dipping a polyamide reverse osmosis membrane in a chitosan mixed solution; transferring to sodium hypochlorite solution for dipping, and putting in sodium bisulfate solution for dipping; and washing with hot water to obtain the composite reverse osmosis membrane. Has the advantages that: (1) adding thionyl chloride and glycerol into a water phase solvent to increase interfacial polymerization; the n-hexane extracting solution is combined for activation, so that the permeability and the salt rejection rate of the polyamide reverse osmosis membrane are effectively improved. (2) The permeability, the desalination rate and the pollution resistance of the composite reverse osmosis membrane are further improved on the basis of ensuring the membrane strength by utilizing the surface modification of chitosan and the oxidation of sodium hypochlorite.
Description
Technical Field
The invention relates to the technical field of reverse osmosis membranes, in particular to a composite reverse osmosis membrane based on a water-soluble polymer and a preparation method thereof.
Background
The reverse osmosis membrane is an artificial semipermeable membrane for separating substances by utilizing the action of higher osmotic pressure than a solution; compared with microfiltration membranes, ultrafiltration membranes and the like, the membrane is a refined mulching film separation product with the retention of more than 0.0001 mu m, and is a core component of reverse osmosis technology; has the characteristics of higher mechanical strength, high efficiency, low energy consumption and the like, is widely used for projects such as seawater desalination, wastewater treatment and the like, and relates to a plurality of fields such as petrochemical industry, medicine, environmental protection, electric power and the like.
The polyamide reverse osmosis membrane is the most commonly used reverse osmosis membrane due to the advantages of high water flux, high chemical stability, high salt rejection rate and the like. However, the membrane pollution caused by microorganisms, organic matters and the like can cause the long-term application of the reverse osmosis membrane, the salt rejection rate and the water flux are reduced, and the energy consumption cost is increased. Therefore, improvement of the stain resistance of polyamide reverse osmosis membranes has been a major research issue. In the prior art, water-soluble polymers such as polyvinyl alcohol and copper polyvinylpyrrolidone are usually modified on the surface of a reverse osmosis membrane so as to obtain hydrophilicity and stain resistance, but the modification has no remarkable improvement on water flux in the practical application process, and the salt rejection rate and the stain resistance are also required to be further improved. On the other hand, there is also a decrease in water flux due to the membrane pore changes caused during the modification process.
Therefore, it is important to prepare a composite reverse osmosis membrane based on a water-soluble polymer to solve the above problems.
Disclosure of Invention
The present invention is directed to a composite reverse osmosis membrane based on a water-soluble polymer and a method for preparing the same, which solves the problems set forth in the background art described above.
In order to solve the technical problems, the invention provides the following technical scheme:
a preparation method of a composite reverse osmosis membrane based on a water-soluble polymer comprises the following steps:
step 1: placing the base support membrane in the aqueous phase solution for dipping for 1-2 minutes, and removing the redundant aqueous phase solution; transferring the mixture into an oil phase solution for interfacial polymerization for 2-3 minutes; activating in n-hexane extractive solution; drying to obtain a polyamide reverse osmosis membrane;
step 2: dipping a polyamide reverse osmosis membrane in a chitosan mixed solution; transferring to sodium hypochlorite solution for dipping, and putting in sodium bisulfate solution for dipping; and washing with hot water to obtain the composite reverse osmosis membrane.
Optimally, in the step 1, the activation time of the n-hexane extracting solution is 1-3 minutes; the drying temperature is 75-82 ℃, and the drying time is 5-8 minutes.
Preferably, in step 1, the preparation method of the aqueous phase solution comprises: mixing m-phenylenediamine, sodium dodecyl benzene sulfonate, thionyl chloride, glycerol and deionized water to form a mixed solution, and adjusting the pH to be 7.2-8.0 by using a camphorsulfonic acid solution and a sodium hydroxide solution to obtain an aqueous phase solution; the preparation method of the oil phase solution comprises the following steps: dissolving trimesoyl chloride solution in Isopa-G solution to obtain oil phase solution with the concentration of 20-25 wt%.
Preferably, the raw materials of the aqueous phase solution comprise the following components: 4-6 parts of m-phenylenediamine, 0.08-0.12 part of sodium dodecyl benzene sulfonate, 8-12 parts of thionyl chloride, 5-8 parts of glycerol and 180-240 parts of deionized water.
Preferably, in step 1, the preparation method of the n-hexane extracting solution comprises the following steps: adding the coated thalli into n-hexane, uniformly mixing, adding linoleic acid, and reacting for 2-4 hours at the temperature of 25-30 ℃; and (4) carrying out centrifugal separation to obtain a normal hexane extracting solution.
Preferably, the linoleic acid accounts for 1-3 v/v% of the n-hexane.
Preferably, in the step 2, the chitosan mixed solution is 0.8-1 g/L of chitosan aqueous solution, and meanwhile, the chitosan mixed solution contains 0.8-1.1 wt% of potassium persulfate; the dipping time is 30-40 minutes.
Preferably, in the step 2, the concentration of the sodium hypochlorite solution is 0.8-1 g/L; the dipping time is 30-40 minutes; the temperature of the hot water is 70-80 ℃.
Preferably, in step 1, the base support membrane includes one or more of a polysulfone support membrane, a polyvinyl chloride support membrane, and a polyvinylidene fluoride support membrane.
In the technical scheme, m-phenylenediamine and trimesoyl chloride are prepared on a basic support membrane by using an interfacial polymerization method, and the water flux and the desalination rate are improved by limiting the parameters of activation and heat treatment. And the chitosan is modified on the surface of the membrane and is combined with a sodium hypochlorite oxidation process, so that the pollution resistance and the permeability of the composite reverse osmosis membrane are further improved on the basis of not influencing the strength of the membrane.
(1) In the scheme, thionyl chloride is added into an aqueous phase solution in the interfacial reaction of m-phenylenediamine and trimesoyl chloride, and the solvent can increase the miscibility of the aqueous phase solution and an oil phase solution and reduce the solubility difference between the two solutions, thereby promoting the interfacial polymerization process. Meanwhile, a certain amount of glycerol is added into the aqueous phase solution, the addition of the glycerol can assist the subsequent oxidation process of sodium hypochlorite, and the glycerol is used for inhibiting the reduction and deformation of the pores of the polyamide reverse osmosis membrane in the drying process and the like of the membrane, so that the porosity is ensured, and the water flux is ensured.
Meanwhile, because the miscibility of the water phase solution and the oil phase solution is increased by the thionyl chloride, the flatness of a two-phase polymerization interface is reduced, and the surface roughness is increased; the synergic glycerol improves the hydrophilicity of the polyamide reverse osmosis membrane and increases the water flux.
(2) In the scheme, Isopa-G is used as an oil phase solution, which is alkane solvent oil with low viscosity and is similar to n-hexane; compared with the solvent which is dissolved by using normal hexane, the solvent can better dissolve trimesoyl chloride in the practical experiment process, thereby better generating the interface reaction. Isopa-G, however, is an isomeric long-chain alkane, all of which have a higher molecular weight than n-hexane, and which, when present in the structure of a polyamide reverse osmosis membrane, results in a decrease in membrane flux. Therefore, in the scheme, a step of activating the n-hexane extractant is added, so that the water flux and the salt rejection rate are further increased; the reason is that: the normal hexane has certain swelling property on the polyamide, so that the polyamide with low molecular weight can be dissolved, and the water flux of the membrane is improved; meanwhile, compared with the activation by using ethanol, the n-hexane is immiscible with salt, so that the salt rejection rate is increased. Of course, a small part of n-hexane molecules remain in the film during the activation process, so the activation time cannot be too long. In addition, the membrane drying process temperature and time should not be too high, and the activation and drying process cannot be replaced, both steps being replaced, which can lead to a flux drop.
(3) In the preparation process of the polyimide permeable membrane, the synergistic action of thionyl chloride and glycerol is utilized to increase the roughness of the surface of the membrane, and although the hydrophilicity can be increased, the pollution is further increased due to the increase of the roughness, so that in order to further improve the hydrophilicity and the pollution resistance, the surface of the polyimide permeable membrane is modified by using chitosan, and then the polyimide permeable membrane is oxidized by using sodium hypochlorite to further modify the polyamide permeable membrane, so that the pollution resistance is increased under the condition that the permeability is not changed. The solubility of sodium hypochlorite in the scheme is 0.8-1 g/L, which is higher than that of the sodium hypochlorite in the conventional method. In general, the increase in sodium hypochlorite concentration damages the polyamide reverse osmosis membrane.
In the scheme, glycerol added in the preparation process can react with sodium hypochlorite to generate substances such as glyceric acid and the like; meanwhile, the adsorption of conjugated linoleic acid on the surface of the membrane in the activation process is utilized, and the substance has oxidation resistance; the two effects make the sodium hypochlorite with higher concentration milder in the polyamide oxidation process, effectively inhibit the excessive oxidation process of the polyamide by the sodium hypochlorite, cause structural damage and reduce the mechanical property.
And the synergistic effect of the conjugated linoleic acid, the chitosan and the glyceric acid effectively improves the hydrophilicity and the salt rejection rate, improves the pollution resistance of the composite reverse osmosis membrane, reduces the deposition thickness of microorganisms, reduces the cleaning frequency of the membrane and prolongs the service life of the composite reverse osmosis membrane. It should be noted that: in this process, the impregnation process of the chitosan solution and the sodium hypochlorite solution cannot be replaced. Performance is directly affected.
Has the advantages that: (1) adding thionyl chloride and glycerol into a water phase solvent to increase interfacial polymerization; the method combines the activation process of the n-hexane extracting solution, so that the permeability and the salt rejection rate of the polyamide reverse osmosis membrane are effectively improved. (2) The surface modification of chitosan and the oxidation of sodium hypochlorite are combined with the conjugated linoleic acid in the glycerol and n-hexane extracting solution in the prior step, so that the permeability, the desalination rate and the pollution resistance of the composite reverse osmosis membrane are further improved on the basis of ensuring the membrane strength.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1:
step 1: (1) mixing 5 parts of m-phenylenediamine, 0.1 part of sodium dodecyl benzene sulfonate, 10 parts of thionyl chloride, 6 parts of glycerol and 210 parts of deionized water to form a mixed solution, and adjusting the pH to be 7.8 by using 0.8wt% of camphorsulfonic acid solution and 0.5wt% of sodium hydroxide solution to obtain an aqueous phase solution; (2) dissolving trimesoyl chloride solution in Isopa-G solution to obtain 24wt% oil phase solution; (3) adding the coated thalli into n-hexane, uniformly mixing, adding 2v/v% of linoleic acid, and reacting for 4 hours at the set temperature of 30 ℃; and (4) carrying out centrifugal separation to obtain a normal hexane extracting solution. (4) Soaking the polysulfone support membrane in the aqueous phase solution for 1.5 minutes, and removing the redundant aqueous phase solution; transferring the solution into an oil phase solution for interfacial polymerization for 2 minutes; activating in n-hexane extracting solution for 2 minutes; drying for 5 minutes at the set temperature of 80 ℃ to obtain a polyamide reverse osmosis membrane;
step 2: (1) adding 1wt% of potassium persulfate into 0.8g/L of chitosan solution to obtain a chitosan mixed solution; (2) placing the polyamide reverse osmosis membrane in the chitosan mixed solution for soaking for 35 minutes; transferring the mixture to sodium chlorate solution of the next 1g/L for soaking for 30 minutes, and placing the mixture in sodium bisulfate solution of 2g/L for soaking for 25 minutes; and washing with hot water at 75 ℃ to obtain the composite reverse osmosis membrane.
Example 2:
step 1: (1) mixing 4 parts of m-phenylenediamine, 0.08 part of sodium dodecyl benzene sulfonate, 8 parts of thionyl chloride, 5 parts of glycerol and 180 parts of deionized water to form a mixed solution, and adjusting the pH to be 7.2 by using 0.8wt% of camphorsulfonic acid solution and 0.5wt% of sodium hydroxide solution to obtain an aqueous phase solution; (2) dissolving trimesoyl chloride solution in Isopa-G solution to obtain oil phase solution with the concentration of 20 wt%; (3) adding the coated thalli into n-hexane, uniformly mixing, adding 1v/v% of linoleic acid, and reacting for 2 hours at the set temperature of 25 ℃; and (4) carrying out centrifugal separation to obtain a normal hexane extracting solution. (4) Soaking the polysulfone support membrane in the aqueous phase solution for 1 minute, and removing the redundant aqueous phase solution; transferring the solution into an oil phase solution for interfacial polymerization for 2 minutes; activating in n-hexane extracting solution for 1 minute; drying for 5 minutes at the set temperature of 75 ℃ to obtain a polyamide reverse osmosis membrane;
step 2: (1) adding 0.8wt% of potassium persulfate into 0.8g/L of chitosan solution to obtain a chitosan mixed solution; (2) soaking the polyamide reverse osmosis membrane in the chitosan mixed solution for 30 minutes; transferring to sodium chlorate solution of 0.8g/L for soaking for 30 minutes, and placing in sodium bisulfate solution of 2g/L for soaking for 20 minutes; washing with hot water at 70 ℃ to obtain the composite reverse osmosis membrane.
Example 3:
step 1: (1) mixing 6 parts of m-phenylenediamine, 0.12 part of sodium dodecyl benzene sulfonate, 12 parts of thionyl chloride, 8 parts of glycerol and 240 parts of deionized water to form a mixed solution, and adjusting the pH to be 8.0 by using 0.8wt% of camphorsulfonic acid solution and 0.5wt% of sodium hydroxide solution to obtain an aqueous phase solution; (2) dissolving trimesoyl chloride solution in Isopa-G solution to obtain oil phase solution with the concentration of 25 wt%; (3) adding the coated thalli into n-hexane, uniformly mixing, adding 3v/v% of linoleic acid, and reacting for 4 hours at the set temperature of 30 ℃; and (4) carrying out centrifugal separation to obtain a normal hexane extracting solution. (4) Soaking the polysulfone support membrane in the aqueous phase solution for 2 minutes, and removing the redundant aqueous phase solution; transferring the solution into an oil phase solution for interfacial polymerization for 3 minutes; activating in n-hexane extracting solution for 3 min; drying for 8 minutes at the set temperature of 82 ℃ to obtain a polyamide reverse osmosis membrane;
step 2: (1) adding 1.1wt% of potassium persulfate into 1g/L of chitosan solution to obtain a chitosan mixed solution; (2) soaking the polyamide reverse osmosis membrane in the chitosan mixed solution for 40 minutes; transferring the mixture to sodium chlorate solution of the next 1g/L for soaking for 40 minutes, and placing the mixture in sodium bisulfate solution of 2g/L for soaking for 30 minutes; and washing with hot water at 80 ℃ to obtain the composite reverse osmosis membrane.
Comparative example 1: replacing the activation and drying steps;
step 1: (1) mixing 5 parts of m-phenylenediamine, 0.1 part of sodium dodecyl benzene sulfonate, 10 parts of thionyl chloride, 6 parts of glycerol and 210 parts of deionized water to form a mixed solution, and adjusting the pH to be 7.8 by using 0.8wt% of camphorsulfonic acid solution and 0.5wt% of sodium hydroxide solution to obtain an aqueous phase solution; (2) dissolving trimesoyl chloride solution in Isopa-G solution to obtain 24wt% oil phase solution; (3) adding the coated thalli into n-hexane, uniformly mixing, adding 2v/v% of linoleic acid, and reacting for 4 hours at the set temperature of 30 ℃; centrifuging to obtain n-hexane extract; (4) soaking the polysulfone support membrane in the aqueous phase solution for 1.5 minutes, and removing the redundant aqueous phase solution; transferring the solution into an oil phase solution for interfacial polymerization for 2 minutes; drying at 80 deg.C for 5 min; activating in n-hexane extracting solution for 2 minutes; obtaining a polyamide reverse osmosis membrane;
step 2: (1) adding 1wt% of potassium persulfate into 0.8g/L of chitosan solution to obtain a chitosan mixed solution; (2) placing the polyamide reverse osmosis membrane in the chitosan mixed solution for soaking for 35 minutes; transferring the mixture to sodium chlorate solution of the next 1g/L for soaking for 30 minutes, and placing the mixture in sodium bisulfate solution of 2g/L for soaking for 25 minutes; and washing with hot water at 75 ℃ to obtain the composite reverse osmosis membrane.
Comparative example 2: no glycerol was added;
step 1: (1) mixing 5 parts of m-phenylenediamine, 0.1 part of sodium dodecyl benzene sulfonate, 10 parts of thionyl chloride and 210 parts of deionized water to form a mixed solution, and adjusting the pH to be 7.8 by using 0.8wt% of camphorsulfonic acid solution and 0.5wt% of sodium hydroxide solution to obtain an aqueous phase solution; (2) dissolving trimesoyl chloride solution in Isopa-G solution to obtain 24wt% oil phase solution; (3) adding the coated thalli into n-hexane, uniformly mixing, adding 2v/v% of linoleic acid, and reacting for 4 hours at the set temperature of 30 ℃; and (4) carrying out centrifugal separation to obtain a normal hexane extracting solution. (4) Soaking the polysulfone support membrane in the aqueous phase solution for 1.5 minutes, and removing the redundant aqueous phase solution; transferring the solution into an oil phase solution for interfacial polymerization for 2 minutes; activating in n-hexane extracting solution for 2 minutes; drying for 5 minutes at the set temperature of 80 ℃ to obtain a polyamide reverse osmosis membrane;
step 2: (1) adding 1wt% of potassium persulfate into 0.8g/L of chitosan solution to obtain a chitosan mixed solution; (2) placing the polyamide reverse osmosis membrane in the chitosan mixed solution for soaking for 35 minutes; transferring the mixture to sodium chlorate solution of the next 1g/L for soaking for 30 minutes, and placing the mixture in sodium bisulfate solution of 2g/L for soaking for 25 minutes; and washing with hot water at 75 ℃ to obtain the composite reverse osmosis membrane.
Comparative example 3: activating without using n-hexane extracting solution;
step 1: (1) mixing 5 parts of m-phenylenediamine, 0.1 part of sodium dodecyl benzene sulfonate, 10 parts of thionyl chloride, 6 parts of glycerol and 210 parts of deionized water to form a mixed solution, and adjusting the pH to be 7.8 by using 0.8wt% of camphorsulfonic acid solution and 0.5wt% of sodium hydroxide solution to obtain an aqueous phase solution; (2) dissolving trimesoyl chloride solution in Isopa-G solution to obtain 24wt% oil phase solution; (3) soaking the polysulfone support membrane in the aqueous phase solution for 1.5 minutes, and removing the redundant aqueous phase solution; transferring the solution into an oil phase solution for interfacial polymerization for 2 minutes; drying for 5 minutes at the set temperature of 80 ℃ to obtain a polyamide reverse osmosis membrane;
step 2: (1) adding 1wt% of potassium persulfate into 0.8g/L of chitosan solution to obtain a chitosan mixed solution; (2) placing the polyamide reverse osmosis membrane in the chitosan mixed solution for soaking for 35 minutes; transferring the mixture to sodium chlorate solution of the next 1g/L for soaking for 30 minutes, and placing the mixture in sodium bisulfate solution of 2g/L for soaking for 25 minutes; and washing with hot water at 75 ℃ to obtain the composite reverse osmosis membrane.
Comparative example 4: activating by using n-hexane instead of n-hexane extracting solution;
step 1: (1) mixing 5 parts of m-phenylenediamine, 0.1 part of sodium dodecyl benzene sulfonate, 10 parts of thionyl chloride, 6 parts of glycerol and 210 parts of deionized water to form a mixed solution, and adjusting the pH to be 7.8 by using 0.8wt% of camphorsulfonic acid solution and 0.5wt% of sodium hydroxide solution to obtain an aqueous phase solution; (2) dissolving trimesoyl chloride solution in Isopa-G solution to obtain 24wt% oil phase solution; (3) soaking the polysulfone support membrane in the aqueous phase solution for 1.5 minutes, and removing the redundant aqueous phase solution; transferring the solution into an oil phase solution for interfacial polymerization for 2 minutes; activating in n-hexane for 2 min; drying for 5 minutes at the set temperature of 80 ℃ to obtain a polyamide reverse osmosis membrane;
step 2: (1) adding 1wt% of potassium persulfate into 0.8g/L of chitosan solution to obtain a chitosan mixed solution; (2) placing the polyamide reverse osmosis membrane in the chitosan mixed solution for soaking for 35 minutes; transferring the mixture to sodium chlorate solution of the next 1g/L for soaking for 30 minutes, and placing the mixture in sodium bisulfate solution of 2g/L for soaking for 25 minutes; and washing with hot water at 75 ℃ to obtain the composite reverse osmosis membrane.
Comparative example 5: exchanging the chitosan solution and the sodium hypochlorite solution in the dipping process;
step 1: (1) mixing 5 parts of m-phenylenediamine, 0.1 part of sodium dodecyl benzene sulfonate, 10 parts of thionyl chloride, 6 parts of glycerol and 210 parts of deionized water to form a mixed solution, and adjusting the pH to be 7.8 by using 0.8wt% of camphorsulfonic acid solution and 0.5wt% of sodium hydroxide solution to obtain an aqueous phase solution; (2) dissolving trimesoyl chloride solution in Isopa-G solution to obtain 24wt% oil phase solution; (3) adding the coated thalli into n-hexane, uniformly mixing, adding 2v/v% of linoleic acid, and reacting for 4 hours at the set temperature of 30 ℃; and (4) carrying out centrifugal separation to obtain a normal hexane extracting solution. (4) Soaking the polysulfone support membrane in the aqueous phase solution for 1.5 minutes, and removing the redundant aqueous phase solution; transferring the solution into an oil phase solution for interfacial polymerization for 2 minutes; activating in n-hexane extracting solution for 2 minutes; drying for 5 minutes at the set temperature of 80 ℃ to obtain a polyamide reverse osmosis membrane;
step 2: (1) adding 1wt% of potassium persulfate into 0.8g/L of chitosan solution to obtain a chitosan mixed solution; (2) soaking the polyamide reverse osmosis membrane in 1g/L sodium hypochlorite solution for 30 minutes; transferring the mixture to a chitosan mixed solution for dipping for 35 minutes, and putting the mixture into a sodium bisulfate solution of 2g/L for dipping for 25 minutes; and washing with hot water at 75 ℃ to obtain the composite reverse osmosis membrane.
Comparative example 6: reducing the concentration of the sodium hypochlorite solution to 0.5 g/L;
step 1: (1) mixing 5 parts of m-phenylenediamine, 0.1 part of sodium dodecyl benzene sulfonate, 10 parts of thionyl chloride, 6 parts of glycerol and 210 parts of deionized water to form a mixed solution, and adjusting the pH to be 7.8 by using 0.8wt% of camphorsulfonic acid solution and 0.5wt% of sodium hydroxide solution to obtain an aqueous phase solution; (2) dissolving trimesoyl chloride solution in Isopa-G solution to obtain 24wt% oil phase solution; (3) adding the coated thalli into n-hexane, uniformly mixing, adding 2v/v% of linoleic acid, and reacting for 4 hours at the set temperature of 30 ℃; and (4) carrying out centrifugal separation to obtain a normal hexane extracting solution. (4) Soaking the polysulfone support membrane in the aqueous phase solution for 1.5 minutes, and removing the redundant aqueous phase solution; transferring the solution into an oil phase solution for interfacial polymerization for 2 minutes; activating in n-hexane extracting solution for 2 minutes; drying for 5 minutes at the set temperature of 80 ℃ to obtain a polyamide reverse osmosis membrane;
step 2: (1) adding 1wt% of potassium persulfate into 0.8g/L of chitosan solution to obtain a chitosan mixed solution; (2) placing the polyamide reverse osmosis membrane in the chitosan mixed solution for soaking for 35 minutes; transferring to sodium chlorate solution of 0.5g/L for soaking for 30 minutes, and placing in sodium bisulfate solution of 2g/L for soaking for 25 minutes; and washing with hot water at 75 ℃ to obtain the composite reverse osmosis membrane.
Experiment: a water-soluble polymer-based composite reverse osmosis membrane prepared in examples and comparative examples was subjected to a performance test. (1) Adding 100ppm bovine serum albumin into 2g/L sodium chloride solution to obtain a test solution; this was measured for water flux and salt rejection at room temperature with a set pressure of 3Mpa and a flow rate of 4LPM, and contamination resistance was obtained by comparing salt rejection and water flux generated after 12 hours. (2) And detecting the elongation at break of the composite reverse osmosis membrane by a mechanical detection instrument. All data are shown in the following table:
and (4) conclusion: the data shown in the table show that: the prepared composite reverse osmosis membrane has good strength after modification, and has excellent water flux and desalination rate. Meanwhile, under the action of a long time, the permeation quantity of the composite reverse osmosis membrane is reduced to a small extent, which shows that the composite reverse osmosis membrane has good pollution resistance.
As can be seen from the data of comparative example 1: when the activation step and the drying step are exchanged, the water flux is reduced obviously because: the thermal process reduces the activation of the polyamide reverse osmosis membrane by the n-hexane extract. It can be seen from the data of comparative example 2 that glycerol was not added, the water flux was reduced, and at the same time, the membrane strength was decreased, because glycerol and thionyl chloride synergistically increased the hydrophilicity in the interfacial polymerization; can react with sodium hypochlorite to generate acid substances in the subsequent oxidation process to increase the hydrophilicity and reduce the peroxidation degree of the polyamide. As can be seen from the data of comparative example 3, the activation flux decreased without using n-hexane extract, and the membrane strength decreased due to: the n-hexane can dissolve micromolecular polyamide, and the conjugated linoleic acid can inhibit peroxidation of the polyamide and increase hydrophilicity. The effect of conjugated linoleic acid was again verified in comparative example 4. The data of comparative example 5 show that the exchange of the two solutions leads to a significant decrease in water flux, while the direct use of high-concentration sodium hypochlorite reduces the strength of the membrane, while the oxidation of chitosan does not occur, which reduces the hydrophilicity. In combination with the data of comparative example 6, it was shown that high concentrations of sodium hypochlorite can enhance hydrophilicity.
In addition, experimental data of comparative examples 2-6 show that the synergistic effect of the conjugated linoleic acid, the chitosan and the glyceric acid effectively improves the pollution resistance of the composite reverse osmosis membrane, reduces the deposition thickness of microorganisms, reduces the cleaning frequency of the membrane and prolongs the service life of the composite reverse osmosis membrane.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. A preparation method of a composite reverse osmosis membrane based on a water-soluble polymer is characterized in that: the method comprises the following steps:
step 1: placing the base support membrane in the aqueous phase solution for dipping for 1-2 minutes, and removing the redundant aqueous phase solution; transferring the mixture into an oil phase solution for interfacial polymerization for 2-3 minutes; activating in n-hexane extractive solution; drying to obtain a polyamide reverse osmosis membrane;
step 2: dipping a polyamide reverse osmosis membrane in a chitosan mixed solution; transferring to sodium hypochlorite solution for dipping, and putting in sodium bisulfate solution for dipping; washing with hot water to obtain a composite reverse osmosis membrane;
the preparation method of the aqueous phase solution comprises the following steps: mixing m-phenylenediamine, sodium dodecyl benzene sulfonate, thionyl chloride, glycerol and deionized water to form a mixed solution, and adjusting the pH to be 7.2-8.0 by using a camphorsulfonic acid solution and a sodium hydroxide solution to obtain an aqueous phase solution; the preparation method of the oil phase solution comprises the following steps: dissolving trimesoyl chloride solution in Isopa-G solution to obtain oil phase solution with the concentration of 20-25 wt%;
the preparation method of the n-hexane extracting solution comprises the following steps: adding the coated thalli into n-hexane, uniformly mixing, adding linoleic acid, and reacting for 2-4 hours at the temperature of 25-30 ℃; and (4) carrying out centrifugal separation to obtain a normal hexane extracting solution.
2. The method of claim 1 for preparing a composite reverse osmosis membrane based on a water soluble polymer, wherein: in the step 1, the activation time of the n-hexane extracting solution is 1-3 minutes; the drying temperature is 75-82 ℃, and the drying time is 5-8 minutes.
3. The method of claim 1 for preparing a composite reverse osmosis membrane based on a water soluble polymer, wherein: the raw materials of the aqueous phase solution comprise the following components: 4-6 parts of m-phenylenediamine, 0.08-0.12 part of sodium dodecyl benzene sulfonate, 8-12 parts of thionyl chloride, 5-8 parts of glycerol and 180-240 parts of deionized water.
4. The method of claim 1 for preparing a composite reverse osmosis membrane based on a water soluble polymer, wherein: the linoleic acid accounts for 1-3 v/v% of the n-hexane.
5. The method of claim 1 for preparing a composite reverse osmosis membrane based on a water soluble polymer, wherein: in the step 2, the chitosan mixed solution is 0.8-1 g/L of chitosan water solution, and meanwhile, 0.8-1.1 wt% of potassium persulfate is contained; the dipping time is 30-40 minutes.
6. The method of claim 1 for preparing a composite reverse osmosis membrane based on a water soluble polymer, wherein: in the step 2, the concentration of the sodium hypochlorite solution is 0.8-1 g/L; the dipping time is 30-40 minutes; the temperature of the hot water is 70-80 ℃.
7. The method of claim 1 for preparing a composite reverse osmosis membrane based on a water soluble polymer, wherein: in the step 1, the base support membrane comprises one or more of a polysulfone support membrane, a polyvinyl chloride support membrane and a polyvinylidene fluoride support membrane.
8. The composite reverse osmosis membrane prepared by the preparation method of the water-soluble polymer-based composite reverse osmosis membrane according to any one of claims 1 to 7.
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